Measurement of the speed of blood coagulation is required for a large portion of the population. Malfunctioning of the coagulation system results in multiple disorders, from hemophilia and bleeding disorders (hemorrhage) to heart attacks and strokes related to unwanted clot formation (thrombosis). Anticoagulant medications are regularly taken by more than 2 million patients in the U.S. and are used during many surgical procedures to prevent blood from clotting in the presence of an open wound in the body.
There are several traditional approaches to the testing of blood coagulation. Two examples of such approaches are prothrombin time (PT) and thromboelastography (TEG). An estimated 800 million PT/INR assays are performed annually worldwide in the lab, together with the near-PT patient testing using CoaguChek. A PT test measures the time at which blood is declared “clotted” after the addition of reagents. The test is performed by moving a magnetic bead in a small amount of coagulating plasma. The moment at which the bead is unable to move is declared the point of coagulation. PT is a relatively inexpensive and fast test that can be performed on numerous samples in parallel. While these attributes are desirable, the test only works on blood plasma and only provides a single data point for the clotting process and therefore does not provide doctors any information about the dynamics of coagulation.
Unlike PT, TEG is capable of extracting additional information that can explain the reasons why something is wrong with the coagulation process. For example, TEG can be used to identify anomalies and show how clot strength is affected by hemophilia, thrombocytopenia, or abnormally strong clot formation. All this additional information is helpful for better diagnostics and monitoring of diseases. Because of this, TEG is considered the “gold standard” method. Unfortunately, the device used to perform TEG is very expensive (e.g., ˜$35,000) and can only simultaneously run two samples with a testing time ranging from 10 to 30 minutes.
From the above discussion, it can be appreciated that it would be desirable to have an alternative way to continuously monitor blood coagulation that is low-cost, simple, sensitive, and capable of working with whole blood.